The effect of organoclay addition on the properties of an acrylate based, thermally activated shape memory polymer

Shape Memory Polymers (SMPs) exhibit the intriguing ability to change back from an intermediate, deformed shape back to their original, permanent shape. In this contribution a systematic series of t-butylacrylate-co-poly(ethyleneglycol) dimethacrylate (tBA-co-PEGDMA) polymers have been synthesised and characterised prior to incorporation of organoclay. Increasing the poly(ethyleneglycol) dimethacrylate (PEGDMA) content in increments of 10% increased the storage modulus from 2005 to 2250 MPa, reduced the glass transition temperature from + 41 to − 26 °C and reduced the intensity of the associated tan δ peak. The tBA-co-PEGDMA crosslinked networks displayed useful shape memory properties up to PEGDMA contents of 40%. Above this PEGDMA percentage the materials were prone to fracture and too brittle for a realistic assessment of their shape memory capability. The system containing 90% t-butylacrylate (tBA) and 10% PEGDMA was selected as the host matrix to investigate how the incorporation of 1 to 5 mass% of a benzyl tallow dimethylammonium-exchanged bentonite (BTDB) influenced the shape memory properties. X-ray diffraction data confirmed that BTDB formed a microcomposite in the selected matrix and exerted no influence on the storage modulus, rubbery modulus, glass transition temperature, Tg, or the shape or intensity of the tan δ peak of the host matrix. Therefore, it was anticipated that the presence of BTDB would have no effect, positive or negative, nor on the shape memory properties of the host matrix. However, it was found that the incorporation of clay, especially at the 1 mass% level, significantly accelerated the speed, compared with the clay-free SMP, at which the microcomposite returned to the original, permanent shape. This accelerated return to the permanent shape was also observed when the microcomposite was coated onto a 100 μm PET film

Adsorption du méthanol par la montmorillonite

International audienc

Nanosized tubular clay minerals: Halloysite and Imogolite

International audienc

Chemistry of nanosized tubular clay minerals

International audienceNatural and synthetic clays and clay minerals are a very big family with different structures, morphologies and properties. Clays, usually kaolins containing mainly kaolinite with laths morphology, are the oldest know pottery materials used in prehistory. As early as 1930, based on observation of the structure of asbestos-related minerals, Pauling proposed the existence of cylindrical structures formed by minerals in nature. This presentation will focus on two examples of such less known rolled clay minerals with tubular nanostructures. These nanosized tubular clay minerals have at least one dimension in the nano range (between 1 and 100 nm) and a hollow tubular structure. Halloysite which is mainly used after extraction from soils has an internal aluminol surface. Imogolite can be also extracted from soils derived from weathered volcanic rocks, has an external aluminol surface. This opposite structural arrangement of the two nanoclay minerals leads to completely different properties. Moreover, halloysite appears very difficult to synthesise but it is easy to prepare synthetic imogolite nanotubes which are monodisperse in diameter (from 2 to 4 nm depending on composition) and polydisperse in length from several tens of nanometers up to several microns. Thanks to microscopic and spectroscopic methods, the structures of some nanosized tubular clay minerals, such as halloysite and imogolite have been identified since the 50's. However, there was very little research on nanosized tubular clay minerals, and relevant papers were published only occasionally. The renewed interest since the 90's in nanosized tubular clay minerals can be partially attributed to the boom in studies on nanostructured materials and related applications, with the first synthesis of carbon nanotubes and several other nanotube materials (e.g., MoS2 and BN). In the context of environmental science and technology, interest has been focused on using these low-cost and environmentally friendly natural materials as adsorbents for remediating pollution. This application is made possible by the high surface activity and amenability to surface modifications for versatile types of pollution treatment